In an existing communications system, each base station has an adaptive retransmission function. When a base station fails to send a data packet to user equipment, the base station resends the data packet to the user equipment, to ensure that the user equipment can properly receive the data packet. The base station uses a radio resource on a same frequency band to initially send the data packet and resend the data packet. Therefore, when initially sending the data packet and scheduling the radio resource for the data packet, the base station needs to consider a radio resource required for retransmitting the data packet, which leads to a relatively complex algorithm for scheduling the radio resource. In addition, because each base station needs to have the adaptive retransmission function, modules such as a retransmission scheduling module and a buffer module needs to be configured for the base station, which leads to a relatively high construction cost of an entire communications system.